// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2003-2011 Jozsef Kadlecsik <kadlec@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/* Get Layer-4 data from the packets */

#include <linux/ip.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/sctp.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <net/ip.h>
#include <net/ipv6.h>

#include <linux/netfilter/ipset/ip_set_getport.h>
#include <linux/export.h>

/* We must handle non-linear skbs */
static bool
get_port(const struct sk_buff *skb, int protocol, unsigned int protooff,
         bool src, __be16 *port, u8 *proto)
{
        switch (protocol) {
        case IPPROTO_TCP: {
                struct tcphdr _tcph;
                const struct tcphdr *th;

                th = skb_header_pointer(skb, protooff, sizeof(_tcph), &_tcph);
                if (!th)
                        /* No choice either */
                        return false;

                *port = src ? th->source : th->dest;
                break;
        }
        case IPPROTO_SCTP: {
                struct sctphdr _sh;
                const struct sctphdr *sh;

                sh = skb_header_pointer(skb, protooff, sizeof(_sh), &_sh);
                if (!sh)
                        /* No choice either */
                        return false;

                *port = src ? sh->source : sh->dest;
                break;
        }
        case IPPROTO_UDP:
        case IPPROTO_UDPLITE: {
                struct udphdr _udph;
                const struct udphdr *uh;

                uh = skb_header_pointer(skb, protooff, sizeof(_udph), &_udph);
                if (!uh)
                        /* No choice either */
                        return false;

                *port = src ? uh->source : uh->dest;
                break;
        }
        case IPPROTO_ICMP: {
                struct icmphdr _ich;
                const struct icmphdr *ic;

                ic = skb_header_pointer(skb, protooff, sizeof(_ich), &_ich);
                if (!ic)
                        return false;

                *port = (__force __be16)htons((ic->type << 8) | ic->code);
                break;
        }
        case IPPROTO_ICMPV6: {
                struct icmp6hdr _ich;
                const struct icmp6hdr *ic;

                ic = skb_header_pointer(skb, protooff, sizeof(_ich), &_ich);
                if (!ic)
                        return false;

                *port = (__force __be16)
                        htons((ic->icmp6_type << 8) | ic->icmp6_code);
                break;
        }
        default:
                break;
        }
        *proto = protocol;

        return true;
}

bool
ip_set_get_ip4_port(const struct sk_buff *skb, bool src,
                    __be16 *port, u8 *proto)
{
        const struct iphdr *iph = ip_hdr(skb);
        unsigned int protooff = skb_network_offset(skb) + ip_hdrlen(skb);
        int protocol = iph->protocol;

        /* See comments at tcp_match in ip_tables.c */
        if (protocol <= 0)
                return false;

        if (ntohs(iph->frag_off) & IP_OFFSET)
                switch (protocol) {
                case IPPROTO_TCP:
                case IPPROTO_SCTP:
                case IPPROTO_UDP:
                case IPPROTO_UDPLITE:
                case IPPROTO_ICMP:
                        /* Port info not available for fragment offset > 0 */
                        return false;
                default:
                        /* Other protocols doesn't have ports,
                         * so we can match fragments.
                         */
                        *proto = protocol;
                        return true;
                }

        return get_port(skb, protocol, protooff, src, port, proto);
}
EXPORT_SYMBOL_GPL(ip_set_get_ip4_port);

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
bool
ip_set_get_ip6_port(const struct sk_buff *skb, bool src,
                    __be16 *port, u8 *proto)
{
        int protoff;
        u8 nexthdr;
        __be16 frag_off = 0;

        nexthdr = ipv6_hdr(skb)->nexthdr;
        protoff = ipv6_skip_exthdr(skb,
                                   skb_network_offset(skb) +
                                        sizeof(struct ipv6hdr), &nexthdr,
                                   &frag_off);
        if (protoff < 0 || (frag_off & htons(~0x7)) != 0)
                return false;

        return get_port(skb, nexthdr, protoff, src, port, proto);
}
EXPORT_SYMBOL_GPL(ip_set_get_ip6_port);
#endif